Mechanical face seals are well known for providing machine protection from severe service environments and allow a rotary shaft to extend from inside a stationary housing to the outside of its housing. However, wearing, corrosion, and large fluctuations in pressure and temperature can often result in face seal failures. Through years, numerous engineering efforts have been made to improve the face seal design assembly in order to increase its reliability and reduce its maintenance cost.
The other known solution is to use magnetic coupling with an air gap to isolate a motor from its load. The fundamental limits of machine using magnetic coupling are its limited torque load, coupling size and heat generation at the coupler. However, there are a lot of industrial machine applications that require high torque and sophisticated controls but lack room to implement the magnetic coupling; or the machine itself is subject to very high external pressure or is under such operating conditions that make the scheduled maintenance services difficult.
The nuclear power plant disaster due to failed backup generators after the big earthquake in Japan in 2011 has urgently raised the need for new generator and pump design that can survive flooding of sea water. The mechanical seal plays a critical role in both waterproof generator and pump design.
Both mechanical face seal and magnetic coupling are suitable for certain types of operating environments and conditions but they are generally not a problem free solution. Nonetheless, overcoming the rotary shaft seal problem is technically challenging. There are many industries including automobile, pump, electrical power generation, marine vessels, aerospace, oilfield services, refinery, chemical plants, food processing, etc. that still need a better seal solution that can transfer rotational motion from an enclosed space to its adjoining spaces or vice versa.
The fundamental mathematical problem in replacing a traditional face seal solution of a rotating shaft is to avoid sealing the infinite periodical boundary conditions that occur between the rotating shaft and the stationary housing, which prevents one from bonding or clamping any seal at this interface.